Various bioreactors used as cell culture devices and artificial organs are known. Typically, the known bioreactors utilize hollow-fiber technology. An array of hollow-fiber reactors exists as filters, membrane oxygenators, plasma separators, and cell line producers.
Commonly, a bundle of small-diameter hollow, porous fibers are contained in a housing that is rigid and sealed. The bundle of fibers is stretched so that the individual fibers run in parallel to each other. The ends of the bundle are sealed at each end so that two compartments are formed: intrafiber that is within the lumens of the fibers and extrafiber that is outside the fibers but still within the housing.
A biological component is loaded into the extrafiber compartment, and a perfusate is typically pumped through the intrafiber compartment. A mass transfer from the intrafiber compartment across the fiber wall into the extrafiber compartment is dependent primarily on convection. During convection, also known as Starling flow, only a small fraction of the perfusate moves to the extrafiber compartment and then returns back to the intrafiber compartment. The driving force behind this phenomenon is a pressure gradient that develops during perfusion along a long axis of the bioreactor. In the known hollow-fiber bioreactors, convection can be increased through the increase in the rate of axial flow.
However, when the conventional hollow-fiber bioreactor is seeded with a biological component, such as, cells, and used as an extracorporeal artificial organ, the rate of axial flow cannot be increased significantly without causing damage to blood cells (hemolysis) and biological component due to excessive sheering pressure.
A need therefore exists for a bioreactor, and a method therefore, that increases the mass transport across the fiber wall under low flow and low pressure conditions.